In many medical procedures, various physiological data within the body of a patient need to be monitored and analyzed. Typically, these data are physical in nature—such as pressure, temperature, and flow rate—and need to be monitored in a safe, reliable and accurate way. In the prior art, it is known to mount a sensor on a guidewire or catheter and to position the sensor via the guidewire in a blood vessel in a living body to detect such a physical parameter. The sensor includes elements that are directly or indirectly sensitive to the parameter. Numerous patents describing different types of sensors for measuring physiological parameters are assigned to the assignee of the present patent specification. For example, temperature can be measured by observing the resistance of a conductor having temperature sensitive resistance as described in U.S. Pat. No. 6,615,067. Another exemplifying sensor may be found in U.S. Pat. No. 6,167,763, in which blood flow exerts pressure on the sensor which delivers a signal representative of the exerted pressure. The entire contents of these patents are incorporated herein by reference for the devices and methods disclosed therein.
The raw signal generated by the sensor located within the body is transmitted to an external device, in which the signal is re-translated into physiological data, which is processed and the results continuously displayed on e.g. a monitor and/or saved. In order to power the sensor and communicate signals representing the measured physiological variable to an external device, one or more cables or leads for transmitting the signals are connected to the sensor, and are routed along the guidewire to be passed out from the vessel to the external device, conventionally via physical cables. In addition, the guidewire is typically provided with a central metal wire (core wire) serving as a support for the sensor and (optionally) also as an electrical connection to the sensor, and a surrounding tubing. Hence, a sensor guidewire typically comprises a core wire, leads and protective tubing, as well as a distal coil or tube and a jacket housing encasing the sensor.
In order to eliminate the risks of having an electrically conductive device such as a pressure transducer connected both to a patient and to an electronic monitoring instrument, a wireless arrangement can be used, e.g. as described in US Patent Application Publication No. 2006/0009817, assigned to the present assignee. In the aforementioned patent application, the pressure sensor wire is adapted to be connected, at its proximal end, to a transceiver unit that is adapted to wirelessly communicate via a communication signal with a communication unit arranged in connection with an external device, in order to transfer measured pressure data to the external device. In addition to the advantage of electrical insulation, a wireless arrangement decreases the amount of cables and other electrical equipment present in the operating room, and also facilitates the use of a standardized communication unit capable of being connected to a wide range of external devices. This obviates the necessity to use a specific external device, possibly different from that which is already present in the operating room. However, in contrast to a conventional sensor guidewire assembly, the pressure sensor in a wireless arrangement is not in electrical connection with the external device. Therefore, an additional energy source is required, such as a battery or capacitor, to power the transceiver unit and the pressure sensor. Also in a wired sensor guidewire assembly, a battery can be used as an alternative or auxiliary power supply. The entire contents of this publication are incorporated herein by reference for the devices and methods disclosed therein.